1. Field of the Invention
The invention relates to an image signal generating apparatus for generating an image signal.
2. Description of the Related Background Art
Hitherto, to display quantized image data, it is once stored into a memory, and when the image data stored in the memory is read out and displayed, the image data compressed by, for instance, a line offset is stored into the memory, and when the image data is read out of the memory, it is expanded by executing an interpolating process and is displayed.
FIG. 1 is an explanatory diagram for explaining the above interpolating process.
It is now assumed that the interpolating process of image data b which has been thinned out by the line offset is performed. Image data a and c existing on both sides of the image data b are compared. When the image data a and c are equal, the portion where the image data b is located is interpolated by the image data a. When the image data a and c are different, the portion where the image data b is located is interpolated by image data d locating on the line just over the line on which the image data b is located. That is, the image data b is determined by decision by majority of the image data a, c, and d.
In the conventional example, however, for instance, the image data is determined by interpolating the image data b by the logic of the decision by majority from the image data a, c, and d compressed by the line offset and is reconstructed. Therefore, in the case where the image data is expanded as mentioned above, the correct image data cannot always be reconstructed by the interpolation, so that there is a case where a request for the superfine image display cannot be satisfied.